1. Field of the Invention
The present invention relates to an image forming technique of forming an image on a print medium.
2. Description of the Related Art
As a technique of correcting density nonuniformity, Japanese Patent Laid-Open No. 02-286341 (reference 1: U.S. Pat. No. 6,045,210) discloses a technique of, when printing an image, detecting density nonuniformity of printing elements at a predetermined timing, and adjusting, based on the detection result, a driving signal to be supplied to a printhead.
Japanese Patent Laid-Open No. 2006-218774 (reference 2) discloses a technique of correcting the print medium conveyance amount on the basis of the result of comparing a test pattern and an image obtained by repeating printing of an image and intermittent conveyance of a print medium in accordance with data obtained by mixing test pattern data in image data.
However, the technique disclosed in reference 1 corrects image data when the number of print sheets reaches a predetermined value or the OFF period reaches a predetermined value. This technique cannot correct density nonuniformity suddenly occurring when forming an image. For this reason, this technique cannot correct image data in real time.
The technique disclosed in reference 2 prints while mixing a test pattern in an image to be printed, and can suppress density nonuniformity caused by a conveyance amount error. However, this technique needs to add a test pattern image to an image to be printed, which may degrade the appearance.